Transporter (TC#) Substrate Intracellular Extracellular
2.A.56.1.6 Sialic acid x  
2.A.80.1.1 Tricarboxylate x  
3.A.1.2.1 Ribose x  
3.A.1.5.12 Rhamnose oligosaccharide   x
4.A.1.1.3 Maltose x  
4.A.2.1.3 2-O-α-Mannosyl-D glycerate   x
4.A.2.1.6 Mannose   x
4.A.2.1.9 Keto sugar x  
4.A.4.1.2 Sugar alcohol (glucitol)   x
4.A.5.1.3 Sugar alcohol (galactitol)   x
4.B.1.1.4 Coenzyme precursor (thiamin) x  
Table 2: A few representative metabolite uptake transporters characteristic of intracellular vs. extracellular pathogens. Adapted from Tang & Saier, 2014